Re: [PATCH V1 11/26] vfio-pci: skip reset during cpr

["Cédric Le Goater" <clg@redhat.com>]

On 1/29/25 15:43, Steve Sistare wrote:
> Do not reset a vfio-pci device during CPR, and do not complain if the
> kernel's PCI config space changes for non-emulated bits between the
> vmstate save and load, which can happen due to ongoing interrupt activity.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>   hw/vfio/pci.c | 37 +++++++++++++++++++++++++++++++++++++
>   1 file changed, 37 insertions(+)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 24ebd69..fa77c36 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -29,6 +29,8 @@
>   #include "hw/pci/pci_bridge.h"
>   #include "hw/qdev-properties.h"
>   #include "hw/qdev-properties-system.h"
> +#include "migration/misc.h"
> +#include "migration/cpr.h"
>   #include "migration/vmstate.h"
>   #include "qapi/qmp/qdict.h"
>   #include "qemu/error-report.h"
> @@ -3324,6 +3326,11 @@ static void vfio_pci_reset(DeviceState *dev)
>   {
>       VFIOPCIDevice *vdev = VFIO_PCI(dev);
>   
> +    /* Do not reset the device during qemu_system_reset prior to cpr load */
> +    if (vdev->vbasedev.reused) {
> +        return;
> +    }
> +

sometime we use :

     MigMode mode = migrate_mode();
     if (mode == MIG_MODE_CPR_TRANSFER) {
         return;
     }

Why is this different ? This is confusing.


Thanks,

C.



>       trace_vfio_pci_reset(vdev->vbasedev.name);
>   
>       vfio_pci_pre_reset(vdev);
> @@ -3447,6 +3454,35 @@ static void vfio_pci_set_fd(Object *obj, const char *str, Error **errp)
>   }
>   #endif
>   
> +/*
> + * The kernel may change non-emulated config bits.  Exclude them from the
> + * changed-bits check in get_pci_config_device.
> + */
> +static int vfio_pci_pre_load(void *opaque)
> +{
> +    VFIOPCIDevice *vdev = opaque;
> +    PCIDevice *pdev = &vdev->pdev;
> +    int size = MIN(pci_config_size(pdev), vdev->config_size);
> +    int i;
> +
> +    for (i = 0; i < size; i++) {
> +        pdev->cmask[i] &= vdev->emulated_config_bits[i];
> +    }
> +
> +    return 0;
> +}
> +
> +static const VMStateDescription vfio_pci_vmstate = {
> +    .name = "vfio-pci",
> +    .version_id = 0,
> +    .minimum_version_id = 0,
> +    .pre_load = vfio_pci_pre_load,
> +    .needed = cpr_needed_for_reuse,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>   static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>   {
>       DeviceClass *dc = DEVICE_CLASS(klass);
> @@ -3457,6 +3493,7 @@ static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>   #ifdef CONFIG_IOMMUFD
>       object_class_property_add_str(klass, "fd", NULL, vfio_pci_set_fd);
>   #endif
> +    dc->vmsd = &vfio_pci_vmstate;
>       dc->desc = "VFIO-based PCI device assignment";
>       set_bit(DEVICE_CATEGORY_MISC, dc->categories);
>       pdc->realize = vfio_realize;